Molds and methods for molding golf balls having a thermoplastic polyurethane cover

ABSTRACT

Golf ball molds and methods for molding golf balls, particularly golf balls having thermoplastic polyurethane covers, are provided. The molds and methods are particularly suitable for manufacturing covers for golf balls. Multi-piece golf balls having inner cores, outer cores, inner covers, and intermediate layers can be made. Retractable pins are used for holding the golf ball within the mold, wherein each retractable pin has a primary vent section, secondary vent section, and tertiary vent section for removing air and other gasses from the interior spherical cavity of the mold.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention generally relates to molds and methods for moldinggolf balls, particularly golf balls having thermoplastic polyurethanecovers. Multi-piece golf balls having inner cores, outer cores, innercovers, and intermediate layers can be made. The finished balls withthermoplastic polyurethane covers have many advantageous physical andplaying performance properties.

Brief Review of the Related Art

Both professional and amateur golfer use multi-piece, solid golf ballstoday. Basically, a two-piece solid golf ball includes a solid innercore protected by an outer cover. The inner core is made of a natural orsynthetic rubber such as polybutadiene, styrene butadiene, orpolyisoprene. The cover surrounds the inner core and may be made of avariety of materials including ethylene acid copolymer ionomers,polyamides, polyesters, polyurethanes, and polyureas.

Three-piece, four-piece, and even five-piece balls have become morepopular over the years. More golfers are playing with these multi-pieceballs for several reasons including new manufacturing technologies,lower material costs, and desirable ball playing performance properties.Many golf balls used today have multi-layered cores comprising an innercore and at least one surrounding outer core layer. For example, theinner core may be made of a relatively soft and resilient material,while the outer core may be made of a harder and more rigid material.The “dual-core” sub-assembly is encapsulated by a single ormulti-layered cover to provide a final ball assembly. Differentmaterials are used in these golf ball constructions to impart specificproperties and playing features to the ball.

For instance, ionomer compositions comprising an ethylene acid copolymercontaining acid groups that are at least partially neutralized can beused to make golf ball covers. Suitable ethylene acid copolymers thatmay be used to form the cover layers are generally referred to ascopolymers of ethylene; C₃ to C₈ α, β-ethylenically unsaturated mono- ordicarboxylic acid; and optional softening monomer. Commerciallyavailable ionomer compositions that can be used to make such coversinclude Surlyn® (DuPont) and Escor® and Iotek® (Exxon) ionomers.

in recent years, there has been high interest in using polyurethanecompositions to make golf ball covers. Basically, polyurethanecompositions contain urethane linkages formed by reacting an isocyanategroup (—N═C═O) with a hydroxyl group (OH). Polyurethanes are produced bythe reaction of a multi-functional isocyanate with a polyol in thepresence of a catalyst and other additives. The chain length of thepolyurethane prepolymer is extended by reacting it withhydroxyl-terminated and amine curing agents.

Different molding operations can be used to form the cover over the coreor sub-assembly of the ball. For example, compression-molding, casting,and injection-molding processes can be use. These molding processesnormally use molds having an upper mold cavity and lower mold cavity.Each mold cavity is hemispherical-shaped and one-half of the size of afinished ball. The mold cavities have interior walls with detailsdefining the dimple pattern of the cover that will be produced. Theupper and lower mold cavities are joined together under sufficient heatand pressure. The polyurethane material in the cavities encapsulates theball subassembly and forms the cover of the ball.

For example, compression-molding typically involves using multiple pairsof mold cavities, each pair comprising first and second mold cavitiesthat mate to form a spherical recess. In one exemplary compressionmolding process, a cover material is pre-formed into half-shells, whichare placed, respectively, into each of a pair of compression moldcavities. The core is placed between the cover material half-shells andthe mold is closed. The core and cover combination is then exposed toheat and pressure, which cause the cover half-shells to combine and forma full cover.

Casting processes also typically use pairs of mold cavities. In acasting process, a cover material is introduced into a first mold cavityof each pair. A core is then either placed directly into the covermaterial or is held in position (e.g., by an overhanging vacuum orsuction apparatus) to contact the cover material in what will be thespherical center of the mold cavity pair. Once the cover material is atleast partially cured (e.g., to a point where the core will notsubstantially move), the cover material is introduced into a second moldcavity of each pair, and the mold is closed. The closed mold is thensubjected to heat and pressure to cure the cover material therebyforming a cover on the core. Casting is a common method used forproducing a thermoset polyurethane cover layer on a golf ball. However,the thermoset polyurethane materials typically used in casting require arelatively long gel time. Long gel times have the disadvantage ofrequiring long cure times for the material to set so that the ball canbe demolded, or removed from the mold. Additionally, once demolded, castgolf balls usually require subsequent buffing and other finishingprocess steps.

Injection molding is a conventional method for forming thermoplasticpolyurethane covers. Injection molding generally utilizes a mold and aninjection unit. The lower mold cavity fits into a lower mold plate(frame) and defines a hemispherical molding cavity for receiving thecore or ball sub-assembly. The plate defines a runner system fortransporting the molten, polyurethane cover material to one or moregates that allow the material to enter the cavity from the runnersystem.

In one example of an injection-molding process, each mold cavity mayalso include retractable positioning pins to hold the core in thespherical center of the mold. Once the core is positioned in the firstmold cavity, the respective second mold cavity is mated to the first toclose the mold. A cover material is then injected into the closed mold.The positioning pins are retracted while the cover material is flowableto allow the material to fill in any holes caused by the pins. When thematerial is at least partially cured, the covered core is removed fromthe mold.

Different molds and molding systems have been used in the past to formgolf ball covers, and these systems have been general effective. Forexample, Puniello et al., U.S. Pat. Nos. 7,223,085; 7,135,138;6,877,974; and 6,235,230 describe different molding systems.

One drawback, however, with using conventional molds and molding systemsis that it can, in some instances, be difficult to ventilate largevolumes of trapped air and other gasses from the mold in a fast manner.It would be desirable to have new, cost-effective, efficient molds andmolding methods that can remove the air and other gasses quickly fromthe interior of the mold. The molds and manufacturing methods alsoshould produce golf balls with good physical and playing performanceproperties. The present invention provides new molds and methods formaking covers for golf balls, particularly thermoplastic polyurethanecovers. The molds and manufacturing methods of this invention arecost-effective and efficient at ventilating air and other gasses andhave other desirable features. The resulting finished golf balls havemany advantageous and properties.

SUMMARY OF THE INVENTION

The present invention generally relates to golf ball molds and methodsfor molding golf balls, particularly golf balls having thermoplasticpolyurethane covers. Multi-piece golf balls having inner cores, outercores, inner covers, and intermediate layers can be made. In oneembodiment, the invention provides a method for molding a golf ball,comprising the steps of: a) providing a mold having a lower mold cavityand upper mold cavity, each mold cavity having an arcuate inner surfacedefining an inverted dimple pattern; so that when the upper and lowermold cavities are mated together, they define a mold having an interiorspherical cavity for holding a golf ball subassembly; b) loading thegolf ball subassembly into the interior spherical cavity of the mold,wherein the mold further includes two or more retractable pins forholding the golf ball within the spherical cavity, each retractable pinhaving a primary vent section, secondary vent section, and tertiary ventsection, the primary vent being in fluid connection with the secondaryvent and the secondary vent being in fluid connection with the tertiaryvent for removing gasses from the interior spherical cavity; c)injecting a polymeric material into the spherical cavity to form aspherical cover over the golf ball sub-assembly; and d) detaching thelower and upper mold cavities and removing the molded golf ball from themold.

Each retractable pin preferably has a free-end planar surface and thepin is movable between an extended position, wherein the free endsurface contacts the ball subassembly and a retracted position whereinthe planar surface forms a portion of the inner wall of the innersurface of the mold cavity. The mold may contain other pins in additionto the retractable pins. For example, the mold may contain a set of highventing inner pins; high venting outer pins; and a stationary highventing center pin.

In one embodiment, the retractable pin has an upper region and theprimary vent is a channel defined along a side of the upper region. Inanother embodiment, the retractable pin has an upper region and theprimary vent is a non-channel and defined along the flat side of theupper region. The upper region of the pin has a diameter that is lessthan the diameter of a bore in the mold cavity for inserting the pin.This primary vent can be referred to as a primary ring vent. A smallcircular gap is created between the upper region of the pin and innersurface of the mold cavity for ventilating the trapped air and othergasses.

In a preferred embodiment, the secondary vent is an elliptical-shapedchannel that is positioned below the primary vent and extends around theperimeter of the retractable pin. This secondary vents acts as anelliptical air reservoir for removing large volumes of gas quickly. Thegasses enter the secondary vent and flow through the elliptical-shapedchannel and around the perimeter of the retractable pin. In oneembodiment, the tertiary vent is a channel that is positioned below thesecondary vent and is defined along a side of the retractable pin.

Preferably, the polymeric material used for making the cover is athermoplastic polyurethane composition. In another example, thepolymeric material is thermoplastic ethylene acid copolymer ionomercomposition. In one example, the ball subassembly comprises a coreformed from a polybutadiene rubber composition. In another example, theball subassembly comprises a core formed from a polybutadiene rubbercomposition, and an intermediate layer formed from an ethylene acidcopolymer ionomer composition.

The present invention also includes molds for forming a golf ball cover,the mold comprising: i) a lower hemispherical-shaped mold cavity; andii) an upper hemispherical-shaped mold cavity; wherein each mold cavityhas an arcuate inner surface defining an inverted dimple pattern; sothat when the upper and lower mold cavities are mated together, theydefine a mold having an interior spherical cavity for holding a golfball subassembly; and each mold cavity comprises at least oneretractable pin for holding the golf ball within the spherical cavity,each retractable pin having a primary vent section, secondary ventsection, and tertiary vent section, the primary vent being in fluidconnection with the secondary vent and the secondary vent being in fluidconnection with the tertiary vent for removing gasses from the interiorspherical cavity. The primary, secondary, and tertiary vents can havethe structures as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features that are characteristic of the present invention areset forth in the appended claims. However, the preferred embodiments ofthe invention, together with further objects and attendant advantages,are best understood by reference to the following detailed descriptionin connection with the accompanying drawings in which:

FIG. 1 is a side view of one embodiment of the lower mold cavity of thepresent invention;

FIG. 2 is a first bottom perspective view of one embodiment of the lowermold cavity of the present invention;

FIG. 3 is a second bottom perspective view of one embodiment of thelower mold cavity of the present invention;

FIG. 4 is a perspective view of one embodiment of the lower mold cavityof the present invention showing the different pins;

FIG. 5 is a top perspective view of the lower mold cavity shown in FIG.4;

FIG. 6 is a perspective view of a retractable pin of the prior art;

FIG. 6A is a perspective view of a first embodiment of a retractable pinof the present invention;

FIG. 7 is a perspective view of a retractable pin of the prior art;

FIG. 7A is a perspective view of a second embodiment of a retractablepin of the present invention;

FIG. 8 is a side view of one embodiment of a retractable pin of thepresent invention;

FIG. 8A is an enlarged view of one portion of the retractable pin shownin FIG. 8 as marked by the Circle “A”.

FIG. 9 is a perspective view of a dimpled golf ball made in accordancewith the present invention;

FIG. 10 is a cross-sectional view of a two-piece golf ball having aninner core and outer cover made in accordance with the presentinvention;

FIG. 11 is a cross-sectional view of another two-piece golf ball havingan inner core and outer cover made in accordance with the presentinvention;

FIG. 12 is a cross-sectional view of a three-piece golf ball having aninner core, outer core, and outer cover made in accordance with thepresent invention;

FIG. 13 is a partial cut-away perspective view of a three-piece golfball having an inner core, outer core, and outer cover made inaccordance with the present invention; and

FIG. 14 is a cross-sectional view of a four-piece golf ball having aninner core, outer core, inner cover, and outer cover made in accordancewith the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates generally to a golf ball mold and a golfball manufacturing method that can be used for molding golf ball coversover a core or ball sub-assembly. In operation, mold cavities (otherwisereferred to as “half-molds” or “mold cups”) are filled with a polymericcover material such as, for example, thermoplastic polyurethane, andjoined together under compressive force to form a spherical cover forthe golf ball.

Golf balls having various constructions may be made in accordance withthis invention. For example, golf balls having three piece, four-piece,and five-piece constructions with single or multi-layered covermaterials may be made. Representative illustrations of such golf ballconstructions are provided and discussed further below. The term,“layer” as used herein means generally any spherical portion of the golfball. More particularly, in one version, a two-piece golf ballcontaining a core and having a surrounding cover is made. Three-piecegolf balls containing a dual-layered core and single-layered cover alsocan be made. The dual-core includes an inner core (center) andsurrounding outer core layer. In another version, a four-piece golf ballcontaining a dual-core and dual-cover (inner cover and outer coverlayers) is made. In yet another construction, a four-piece or five-piecegolf ball containing a dual-core; casing layer(s); and cover layer(s)may be made. As used herein, the term, “casing layer” means a layer ofthe ball disposed between the multi-layered core sub-assembly and cover.The casing layer also may be referred to as a mantle or intermediatelayer. The diameter and thickness of the different layers along withproperties such as hardness and compression may vary depending upon theconstruction and desired playing performance properties of the golf ballas discussed further below.

Mold Cavities

Referring to the drawings, where like reference numerals are used todesignate like elements, FIG. 1 illustrates one embodiment of a moldgenerally indicated at (10) of the present invention. A mold frame orplate is part of the mold (10) and one plate is referred to as the“lower” plate and the corresponding plate (not shown) is referred to asthe “upper” plate herein for purposes of describing the position of theplates based on one perspective. The mold plate has a recessed portionfor holding the lower mold cavity (12). The mold plate can beconstructed to hold one or multiple mold cavities. Although the viewsshown in the Figures are primarily of a lower mold cavity (12), itshould be understood the components of the upper mold plate and moldcavity will have a similar structure and configuration. Also, it shouldbe understood the terms, “lower”, “upper”, “bottom”, “top”, “right”,“left”, “middle” and the like are arbitrary terms used to refer to oneposition of an element based on one perspective and should not beconstrued as limiting the scope of the invention.

The mold (10) comprises hemispherical-shaped lower and upper moldcavities having interior dimple patterns. One example of a lower moldcavity (12) is shown in FIG. 1. The upper mold cavity is not shown inFIG. 1, but it is recognized that it will have a similar structure. Eachmold cavity has an arcuate inner surface defining an inverted dimplepattern. Various geometrical dimple patterns may be used in accordancewith this invention as discussed further below. The mold cavitiesinclude hemispherical bases that are constructed so they fit into therecessed portions of the respective mold plates. Preferably, the moldcavities are made from a metal material, for example, stainless steel,brass, or silicon bronze. These metals provide the mold cavities withhigh durability, mechanical strength, and efficient thermal transfer.The metal mold cavities can withstand higher pressures and temperatureswithout deforming. When the lower and upper mold cavities are joinedtogether, they define an interior spherical cavity that forms the coverfor the ball. The cover material in the mold cavities adheres to thegolf ball subassembly to form a unitary and integral cover structure.The ball sub-assembly refers to the core structure and any intermediatelayers disposed about the core such as casing, mantle, or intermediatelayers. Such core and ball subassembly structures are further describedbelow.

The cover material encapsulates the inner ball to provide a surroundingcover layer. Furthermore, the cover material conforms to the interiorgeometry of the mold cavities to form a dimple pattern on the surface ofthe ball. The mold cavities are mated together along a parting line thatcreates an equator or seam for the finished ball. Different partinglines and dimple patterns may be used to make the ball as discussedfurther below.

As shown in FIGS. 4 and 5, in one embodiment, the mold (10) contains aset of four stationary high venting inner pins (20, 22, 24, and 26);four stationary high venting outer pins (30, 32, 34, and 36); fourretractable high venting pins (40, 42, 44, and 46); and one stationaryhigh venting center pin (50).

Although the molds (10) are described primarily herein as containing theabove-described number of venting pins, it should be understood that themold (10) may be constructed so as to contain any suitable number ofventing pins. The number and configuration of venting pins areunlimited. The mold (10) with the venting pins shown in FIGS. 4 and 5represents only one example of a mold that can be used in this inventionand other mold designs can be used without departing from the spirit andscope of this invention.

Referring to FIGS. 2 and 3, the back surface (55) of the mold cavitydefines bores (60) for each pin (40, 42, 44, and 46) so that the pinsextend there through and are affixed thereto. The retractable pins andother pins contact the core (not shown) in generally the pole area ofthe core. The pins are activated by plates (not shown) that controlmovement of pins to engage with core to hold it securely in place. Theplates may be actuated in a variety of manners known within the art,such as hydraulically or pneumatically.

When the upper and lower mold plates and the upper and lower moldcavities are separated, the core or ball subassembly (not shown) isplaced within the lower cavity on the pins, and the mold plates areclosed to form a spherical cavity around the core. The pins center thecore in the spherical cavity during molding. Then, the injection unit(not shown) forces the molten, cover material through a runner systemand gates (not shown) into the molding cavity, until the cavity isfilled and the material surrounds the core or ball subassembly.Different injection-molding gates can be used in accordance with thepresent invention; and the amount of gates can vary also. For example,twelve (12) injection-molding gates can be used, and in one preferredembodiment, twenty (20) injection-molding gates can be used per thisinvention. Preferably, ring injection-molding gates, as described inPuniello, U.S. Pat. No. 6,235,230, the disclosure of which is herebyincorporated by reference, is used. The retractable pins begin toretract as the molten material comes into close proximity to the pins.The molten material flows and fills the area or voids in the materialcaused by the pins. The dimples at the positions of the retractable pinsare formed at this time by the dimple-forming surfaces on the end facesof the pins. That is, the retractable pins are located where a dimplewill be formed on the outer cover of the ball. The free-end planarsurfaces of the retractable pins are shaped to form the dimple. As thecover material cools, it solidifies in the shape of the mold around thecore or ball subassembly to form the cover of the golf ball. When thecover material is sufficiently cool, the ball is ejected from the mold.Then, the mold is made ready for another molding cycle.

The retractable pins center the core within the spherical cavity so thatthe core is spaced away from the mold cavities' internal surfaces. Theretractable pins are movable between an extended position (moving intothe mold) and a retracted position (moving out of the mold). In theextended position, the pins contact the core. In the retracted position,the pins are flush with the mold cavity surfaces. Referring back toFIGS. 1-5, the retractable pins (40, 42, 44, and 46) extend from thelower half in a first direction into the lower mold cavity (12). The setof retractable pins in lower half the are aligned with the associatedset of pins in the upper half (not shown). In another embodiment, thesets of pins can be unaligned.

The upper and lower mold cavities move between open and closedpositions. In the open position, the mold cavities are spaced apart. Inthe closed position, the planar surfaces of the mold cavities are incontact except at gates. In this position, the upper and lower moldcavities form an internal, spherical molding cavity. The gates areopenings through which molten material enters the spherical cavity fromthe runners or passageways.

With the pins in the extended position, the core is placed between thepins so that the core is centered within the cavities. An injection unit(not shown) forces the molten material into the spherical cavity. Thiscontinues until enough of the molten material has been injected to coverthe core. After the molten material contacts the core, the pins areretracted. Retraction continues until the free ends of the pins form aportion of the mold cavities. The free end surfaces of the pins areshaped or textured to conform to the radius and negative dimple patternof the golf ball mold cavity. Then, the molten material solidifies toform the cover layer.

Retractable Pins

As shown in FIG. 6, a conventional retractable pin (64) is shown. Theplanar top end-face (66) of the pin is angled so that it defines aportion of the inner wall of the mold cavity when the pin is in aretracted position. Thus, the surface (66) of the pin often has anelliptical-shape when seen from a top view. The retractable pin (64)also includes primary vents (68) and secondary vents (70) extendingalong the outer surface of the pin. The primary vents (68) arerelatively narrow channels or grooves located at the upper region of thepin (64). These narrow primary vent flats (68) extend from the tip(planar top end-face) of the pin (64). Meanwhile, the secondary vents(70) are channels or grooves located below the primary vents (68) andtypically have wider and deeper openings so that trapped air and othergasses can be released from the mold after escaping from the mold cavitythrough the primary vents. Such traditional retractable pins (64) mayhave staggered vent depths to allow for consistent back pressure aroundthe contour of the pin head. However, there are still some drawbackswith these traditional retractable pins. For example, these conventionalretractable pins (64) having staggered vent depths are made by machiningthe vents in the pins, and this machining process can be difficultespecially when precise vent depths must be generated. Also, astraditional retractable pins (64) are retracted from the mold, the pinscan draw the cover material into the pin clearances and mold. There alsocan be substantial wear between the retractable pins (64) and mold.These forces can cause excessive flash material and surface defects toappear on the cover surface of the ball.

Referring to FIG. 6A, in the present invention, the retractable pinassembly (74) also has an elliptical-shaped free-end planar top surface(76) when seen from a top view. The retractable pin assembly alsocomprises primary vents (78). The primary vents (78) allow trapped airand other gasses to quickly escape the mold as the flow front of themolten cover material advances toward the poles. In one embodiment, theprimary vents (78) are relatively narrow channels or grooves located atthe upper region of the pin (74). These narrow primary vents (68) extendfrom the tip (planar top end-face) of the pin (74). These primary vents(78) are formed on the side edges of the retractable pin, and thesechannels are sufficiently wide to allow trapped air and gasses to escapethe mold cavity, but the channels also are sufficiently narrow toprevent flash from forming. In one example, the primary vents (78) havea depth is in the range of about about 0.0003 inches to about 0.003inches. The retractable pin assembly (74) can have a single or multipleprimary vents (78); for example, the pin assembly can have 3, 4, 5, 6,or 7 vent channels in some instances. In other embodiments, the primaryvent of the retractable pin (74) can be a ring vent as described furtherbelow.

As shown in FIG. 6A, the primary vents (78) channel the escaping air andother gasses to an elliptical air/gas reservoir (80) and then totertiary vents (82) so that the air/gasses are exhausted from the mold.The distance between the primary vents (78) and elliptical air reservoir(80) is relatively small. The elliptical air reservoir (80) can bereferred to as a secondary vent in this embodiment of the invention.However, it should be understood that the elliptical air reservoir (80)shown in FIG. 6A has a very different structure and functions verydifferently than the linear secondary vents (70) located on the outersurface of conventional retractable pins (64) as discussed above andillustrated in FIG. 6. The elliptical air reservoir (secondary vent)(80) has an elliptical shape so that large volumes of air and othergasses can flow more quickly and be removed from the mold. Theair/gasses flow in an elliptical pattern around the elliptical pathwayof the secondary vent (80) of the present invention. This ellipticalchannel (80) provides full venting of the air/gasses around the fullperimeter of the pin (74). The air/gasses are then exhausted intotertiary vents (82) to minimize any back pressure and resistance to theair/gas flow and to provide relief of the air/gas pressure. For example,the flow front of the molten material can advance from the gates to thepoles in about 0.2 to about 1.0 seconds. After passing through thenarrow openings at the tips of the primary vents (78), the air and othergasses are released from the mold through the elliptical secondary vent(80) and through the tertiary vents (82).

Referring to FIG. 7, another view of the conventional retractable pin(64) in FIG. 6 is shown. Referring to FIG. 7A, a second embodiment ofthe retractable pin assembly (86) of the present invention is shown. Theretractable pin assembly (86) shown in FIG. 7A also has anelliptical-shaped free-end planar surface (87) when seen from a topview. The retractable pin assembly (74) comprises a primary ring vent(90), an elliptical-shaped air reservoir (which can be referred to as asecondary vent in this embodiment) (80); and a tertiary vent (82).

In this embodiment of a primary ring vent (90), the free-end planar face(87) and upper region (90) of the retractable pin (86) are preciselyground to a very small diameter. Thus, the relatively small diameterupper region of the retractable pin (74) can be referred to as a ringvent (90). In one example, the diameter of the ring vent (90) can besmaller than the bore size for the retractable pin located on the backside of the cavity (indicated at 60 in FIG. 3) by a factor of about0.002 to about 0.0002 inches. Thus, the diameter of the primary ringvent (90) is such that a small circular gap is created between thisupper region (90) of the retractable pin and the retractable pin bore(60). Trapped air and other gasses can escape the inside of the moldcavity through this ring vent (90). In some examples, the venting of thetrapped air/gasses through this ring vent (90) can be substantiallygreater than the venting of the air/gasses through the vents formed onthe side edges of the retractable pin (that is, the primary vents (78))described above.

In this example, the primary ring vent (90) is in fluid communicationwith an elliptical-shaped air reservoir (secondary vent) (80); and theelliptical air reservoir (80) is in fluid communication with thetertiary vent (82). The tertiary vent (82) may be a channel formed alongthe outer side surfaces of the pin (74).

The retractable pin (86) can have any suitable dimensions. For example,referring to FIGS. 8 and 8A, the overall length (L1) of the retractablepin assembly (86) can be in the range of about 1.500 to about 3.500inches. The height (H1) between the planar elliptical-shaped free-endface (87) of the retractable pin (86) and the elliptical-shaped airreservoir (secondary vent) (80) can be any suitable distance, forexample, it can be in the range of about 0.050 to about 0.150 inches.Also, the elliptical air reservoir (80) can have any suitabledimensions. For example, in one embodiment, the radius of elliptical airreservoir (80) (R1) can be in the range of about 0.020 to about 0.200inches, while the height (H2) of the elliptical air reservoir (80) canbe in the range of 0.010 to about 0.110 inches. It is understood thatthe dimensions of the retractable pin assembly (86) can vary inaccordance with this invention.

Although the structures and functions of the primary vents, secondaryvents, and tertiary vents of this invention are described andillustrated primarily herein by referring to the retractable ventingpins as shown in FIGS. 6A and 7A, it is understood that other ventingpins in the mold can have such vent structures and functions. Forexample, any or all of the above-described stationary high venting innerpins (20, 22, 24, and 26); stationary high venting outer pins (30, 32,34, and 36); and stationary high venting center pin (50) can have suchprimary, secondary, and tertiary vent structures in accordance with thepresent invention.

One problem with conventional retractable pins is that it often takes asubstantial amount of time to ventilate the trapped air and other gassesand this can cause surface defects on the newly formed golf ball coverlayer. The mold of this invention which includes the above-describedretractable pins with the elliptical-shaped air reservoir has manyadvantages over molds containing conventional retractable pins includingthe ability to ventilate large volumes of the air and other gasses veryquickly. In the mold of the present invention, the trapped air andgasses are dumped rapidly into the elliptical air reservoir and removedfrom the mold. The distance between the primary vents and secondaryvents is relatively small; and the secondary vent has an ellipticalshape so that large volumes of air can flow more quickly. The air canflow around the elliptical air reservoir of the pin assembly. The airflows in an elliptical pattern around the elliptical pathway of thereservoir. This elliptical channel provides full venting of theair/gasses around the full perimeter of the pin. The air/gasses flowsalong the elliptical pathway of the secondary vent so that there is fullelliptical venting of the air/gasses. At the same time, the distancebetween the primary vent and secondary vent remains constant. Thestructure of the retractable pin assembly of this invention helpsprovide fast venting of large volumes of the trapped air and gasses.This helps to provide a high quality golf ball cover having gooddurability. The molds and molding methods of this invention helps reducethe amount of flash material and reduces dimple distortions and othersurface imperfections on the cover of the ball. The molds and moldingmethods of this invention also have other advantageous properties,features, and benefits.

The molds and manufacturing methods of this invention can be used toproduce balls having good impact durability and cut/shear-resistance.The covers have high mechanical strength and cut/shear-resistance. Atthe same time, the molds can be used to make relatively thin outer coverlayers and this means that a player will have a more comfortable andnatural feeling when hitting the ball with a club. The cover layer mayprovide the balls with a softer feel. As described further below, anysuitable polymeric material can be used to form the cover layers for theballs. Thermoplastic polyurethane compositions are particularlypreferred for making the cover. Other suitable cover compositionsinclude ethylene acid copolymer ionomers. Various golf ballconstructions and compositions are described further below. Theseinclude multi-piece golf balls having inner cores, outer cores, innercovers, and intermediate layers.

Core Structure

The golf ball may contain a single- or multi-layered core. In onepreferred embodiment, at least one of the core layers is formed of arubber composition comprising polybutadiene rubber material. Moreparticularly, in one version, the ball contains a single inner coreformed of the polybutadiene rubber composition. In a second version, theball contains a dual-core comprising an inner core (center) andsurrounding outer core layer.

In one version, the core is formed of a rubber composition comprising arubber material such as, for example, polybutadiene, ethylene-propylenerubber, ethylene-propylene-diene rubber, polyisoprene, styrene-butadienerubber, polyalkenamers, butyl rubber, halobutyl rubber, or polystyreneelastomers. For example, polybutadiene rubber compositions may be usedto form the inner core (center) and surrounding outer core layer in adual-layer construction. In another version, the core may be formed froman ionomer composition comprising an ethylene acid copolymer containingacid groups such that greater than 70% of the acid groups areneutralized. These highly neutralized polymers (HNPs) also may be usedto form at least one core layer in a multi-layered core construction.For example, a polybutadiene rubber composition may be used to form thecenter and a HNP composition may be used to form the outer core. Suchrubber and HNP compositions are discussed in further detail below.

In general, polybutadiene is a homopolymer of 1, 3-butadiene. The doublebonds in the 1, 3-butadiene monomer are attacked by catalysts to growthe polymer chain and form a polybutadiene polymer having a desiredmolecular weight. Any suitable catalyst may be used to synthesize thepolybutadiene rubber depending upon the desired properties. Normally, atransition metal complex (for example, neodymium, nickel, or cobalt) oran alkyl metal such as alkyllithium is used as a catalyst. Othercatalysts include, but are not limited to, aluminum, boron, lithium,titanium, and combinations thereof. The catalysts produce polybutadienerubbers having different chemical structures. In a cis-bondconfiguration, the main internal polymer chain of the polybutadieneappears on the same side of the carbon-carbon double bond contained inthe polybutadiene. In a trans-bond configuration, the main internalpolymer chain is on opposite sides of the internal carbon-carbon doublebond in the polybutadiene. The polybutadiene rubber can have variouscombinations of cis- and trans-bond structures. A preferredpolybutadiene rubber has a 1,4 cis-bond content of at least 40%,preferably greater than 80%, and more preferably greater than 90%. Ingeneral, polybutadiene rubbers having a high 1,4 cis-bond content havehigh tensile strength. The polybutadiene rubber may have a relativelyhigh or low Mooney viscosity.

Examples of commercially-available polybutadiene rubbers that can beused in accordance with this invention, include, but are not limited to,BR 01 and BR 1220, available from BST Elastomers of Bangkok, Thailand;SE BR 1220LA and SE BR1203, available from DOW Chemical Co of Midland,Mich.; BUDENE 1207, 1207s, 1208, and 1280 available from Goodyear, Incof Akron, Ohio; BR 01, 51 and 730, available from Japan Synthetic Rubber(JSR) of Tokyo, Japan; BUNA CB 21, CB 22, CB 23, CB 24, CB 25, CB 29MES, CB 60, CB Nd 60, CB 55 NF, CB 70 B, CB KA 8967, and CB 1221,available from Lanxess Corp. of Pittsburgh. Pa.; BR1208, available fromLG Chemical of Seoul, South Korea; UBEPOL BR130B, BR150, BR150B, BR150L,BR230, BR360L, BR710, and VCR617, available from UBE Industries, Ltd. ofTokyo, Japan; EUROPRENE NEOCIS BR 60, INTENE 60 AF and P30AF, andEUROPRENE BR HV80, available from Polimeri Europa of Rome, Italy; AFDENE50 and NEODENE BR40, BR45, BR50 and BR60, available from Karbochem (PTY)Ltd. of Bruma, South Africa; KBR 01, NdBr 40, NdBR-45, NdBr 60, KBR710S, KBR 710H, and KBR 750, available from Kumho Petrochemical Co.,Ltd. Of Seoul, South Korea; and DIENE 55NF, 70AC, and 320 AC, availablefrom Firestone Polymers of Akron, Ohio.

To form the core, the polybutadiene rubber is used in an amount of atleast about 5% by weight based on total weight of composition and isgenerally present in an amount of about 5% to about 100%, or an amountwithin a range having a lower limit of 5% or 10% or 20% or 30% or 40% or50% and an upper limit of 55% or 60% or 70% or 80% or 90% or 95% or100%. In general, the concentration of polybutadiene rubber is about 45to about 95 weight percent. Preferably, the rubber material used to formthe core layer comprises at least 50% by weight, and more preferably atleast 70% by weight, polybutadiene rubber.

The rubber compositions of this invention may be cured, either bypre-blending or post-blending, using conventional curing processes.Suitable curing processes include, for example, peroxide-curing,sulfur-curing, high-energy radiation, and combinations thereof.Preferably, the rubber composition contains a free-radical initiatorselected from organic peroxides, high energy radiation sources capableof generating free-radicals, and combinations thereof. In one preferredversion, the rubber composition is peroxide-cured. Suitable organicperoxides include, but are not limited to, dicumyl peroxide;n-butyl-4,4-di(t-butylperoxy) valerate;1,1-di(t-butylperoxy)3,3,5-trimethylcyclohexane;2,5-dimethyl-2,5-di(t-butylperoxy) hexane; di-t-butyl peroxide;di-t-amyl peroxide; t-butyl peroxide; t-butyl cumyl peroxide;2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3;di(2-t-butyl-peroxyisopropyl)benzene; dilauroyl peroxide; dibenzoylperoxide; t-butyl hydroperoxide; and combinations thereof. In aparticular embodiment, the free radical initiator is dicumyl peroxide,including, but not limited to Perkadox® BC, commercially available fromAkzo Nobel. Peroxide free-radical initiators are generally present inthe rubber composition in an amount of at least 0.05 parts by weight per100 parts of the total rubber, or an amount within the range having alower limit of 0.05 parts or 0.1 parts or 1 part or 1.25 parts or 1.5parts or 2.5 parts or 5 parts by weight per 100 parts of the totalrubbers, and an upper limit of 2.5 parts or 3 parts or 5 parts or 6parts or 10 parts or 15 parts by weight per 100 parts of the totalrubber. Concentrations are in parts per hundred (phr) unless otherwiseindicated. As used herein, the term, “parts per hundred,” also known as“phr” or “pph” is defined as the number of parts by weight of aparticular component present in a mixture, relative to 100 parts byweight of the polymer component. Mathematically, this can be expressedas the weight of an ingredient divided by the total weight of thepolymer, multiplied by a factor of 100.

The rubber compositions preferably include a reactive cross-linkingco-agent. Suitable co-agents include, but are not limited to, metalsalts of unsaturated carboxylic acids having from 3 to 8 carbon atoms;unsaturated vinyl compounds and polyfunctional monomers (e.g.,trimethylolpropane trimethacrylate); phenylene bismaleimide; andcombinations thereof. Particular examples of suitable metal saltsinclude, but are not limited to, one or more metal salts of acrylates,diacrylates, methacrylates, and dimethacrylates, wherein the metal isselected from magnesium, calcium, zinc, aluminum, lithium, and nickel.In a particular embodiment, the co-agent is selected from zinc salts ofacrylates, diacrylates, methacrylates, and dimethacrylates. In anotherparticular embodiment, the agent is zinc diacrylate (ZDA). When theco-agent is zinc diacrylate and/or zinc dimethacrylate, the co-agent istypically included in the rubber composition in an amount within therange having a lower limit of 1 or 5 or 10 or 15 or 19 or 20 parts byweight per 100 parts of the total rubber, and an upper limit of 24 or 25or 30 or 35 or 40 or 45 or 50 or 60 parts by weight per 100 parts of thebase rubber.

Radical scavengers such as a halogenated organosulfur or metal saltthereof, organic disulfide, or inorganic disulfide compounds may beadded to the rubber composition. These compounds also may function as“soft and fast agents.” As used herein, “soft and fast agent” means anycompound or a blend thereof that is capable of making a core: 1) softer(having a lower compression) at a constant “coefficient of restitution”(COR); and/or 2) faster (having a higher COR at equal compression), whencompared to a core equivalently prepared without a soft and fast agent.Preferred halogenated organosulfur compounds include, but are notlimited to, pentachlorothiophenol (PCTP) and salts of PCTP such as zincpentachlorothiophenol (ZnPCTP). Using PCTP and ZnPCTP in golf ball innercores helps produce softer and faster inner cores. The PCTP and ZnPCTPcompounds help increase the resiliency and the coefficient ofrestitution of the core. In a particular embodiment, the soft and fastagent is selected from ZnPCTP, PCTP, ditolyl disulfide, diphenyldisulfide, dixylyl disulfide, 2-nitroresorcinol, and combinationsthereof.

The rubber compositions of the present invention also may include“fillers,” which are added to adjust the density and/or specific gravityof the material. Suitable fillers include, but are not limited to,polymeric or mineral fillers, metal fillers, metal alloy fillers, metaloxide fillers and carbonaceous fillers. The fillers can be in anysuitable form including, but not limited to, flakes, fibers, whiskers,fibrils, plates, particles, and powders. Rubber regrind, which isground, recycled rubber material (for example, ground to about 30 meshparticle size) obtained from discarded rubber golf ball cores, also canbe used as a filler. The amount and type of fillers utilized aregoverned by the amount and weight of other ingredients in the golf ball,since a maximum golf ball weight of 45.93 g (1.62 ounces) has beenestablished by the United States Golf Association (USGA).

Suitable polymeric or mineral fillers that may be added to the rubbercomposition include, for example, precipitated hydrated silica, clay,talc, asbestos, glass fibers, aramid fibers, mica, calcium metasilicate,barium sulfate, zinc sulfide, lithopone, silicates, silicon carbide,tungsten carbide, diatomaceous earth, polyvinyl chloride, carbonatessuch as calcium carbonate and magnesium carbonate. Suitable metalfillers include titanium, tungsten, aluminum, bismuth, nickel,molybdenum, iron, lead, copper, boron, cobalt, beryllium, zinc, and tin.Suitable metal alloys include steel, brass, bronze, boron carbidewhiskers, and tungsten carbide whiskers. Suitable metal oxide fillersinclude zinc oxide, iron oxide, aluminum oxide, titanium oxide,magnesium oxide, and zirconium oxide. Suitable particulate carbonaceousfillers include graphite, carbon black, cotton flock, natural bitumen,cellulose flock, and leather fiber. Micro balloon fillers such as glassand ceramic, and fly ash fillers can also be used. In a particularaspect of this embodiment, the rubber composition includes filler(s)selected from carbon black, nanoclays (e.g., Cloisite® and Nanofil®nanoclays, commercially available from Southern Clay Products, Inc., andNanomax® and Nanomer® nanoclays, commercially available from Nanocor,Inc.), talc (e.g., Luzenac HAR® high aspect ratio talcs, commerciallyavailable from Luzenac America, Inc.), glass (e.g., glass flake, milledglass, and microglass), mica and mica-based pigments (e.g., Iriodin®pearl luster pigments, commercially available from The Merck Group), andcombinations thereof. In a particular embodiment, the rubber compositionis modified with organic fiber micropulp.

In addition, the rubber compositions may include antioxidants to preventthe breakdown of the elastomers. Also, processing aids such as highmolecular weight organic acids and salts thereof, may be added to thecomposition. In a particular embodiment, the total amount of additive(s)and filler(s) present in the rubber composition is 15 wt % or less, or12 wt % or less, or 10 wt % or less, or 9 wt % or less, or 6 wt % orless, or 5 wt % or less, or 4 wt % or less, or 3 wt % or less, based onthe total weight of the rubber composition.

The polybutadiene rubber material (base rubber) may be blended withother elastomers in accordance with this invention. Other elastomersinclude, but are not limited to, polybutadiene, polyisoprene, ethylenepropylene rubber (“EPR”), styrene-butadiene rubber, styrenic blockcopolymer rubbers (such as “SI”, “SIS”, “SB”, “SBS”, “SIBS”, and thelike, where “S” is styrene, “I” is isobutylene, and “B” is butadiene),polyalkenamers such as, for example, polyoctenamer, butyl rubber,halobutyl rubber, polystyrene elastomers, polyethylene elastomers,polyurethane elastomers, polyurea elastomers, metallocene-catalyzedelastomers and plastomers, copolymers of isobutylene and p-alkylstyrene,halogenated copolymers of isobutylene and p-alkylstyrene, copolymers ofbutadiene with acrylonitrile, polychloroprene, alkyl acrylate rubber,chlorinated isoprene rubber, acrylonitrile chlorinated isoprene rubber,and combinations of two or more thereof.

The polymers, free-radical initiators, filler, cross-linking agents, andany other materials used in forming either the golf ball center or anyportion of the core, in accordance with invention, may be combined toform a mixture by any type of mixing known to one of ordinary skill inthe art. Suitable types of mixing include single pass and multi-passmixing, and the like. The cross-linking agent, and any other optionaladditives used to modify the characteristics of the golf ball center oradditional layer(s), may similarly be combined by any type of mixing. Asingle-pass mixing process where ingredients are added sequentially ispreferred, as this type of mixing tends to increase efficiency andreduce costs for the process. The preferred mixing cycle is single stepwherein the polymer, cis-to-trans catalyst, filler, zinc diacrylate, andperoxide are added in sequence.

In one preferred embodiment, the entire core or at least one core layerin a multi-layered structure is formed of a rubber compositioncomprising a material selected from the group of natural and syntheticrubbers including, but not limited to, polybutadiene, polyisoprene,ethylene propylene rubber (“EPR”), ethylene-propylene-diene (“EPDM”)rubber, styrene-butadiene rubber, styrenic block copolymer rubbers (suchas “SI”, “SIS”, “SB”, “SBS”, “SIBS”, and the like, where “S” is styrene,“I” is isobutylene, and “B” is butadiene), polyalkenamers such as, forexample, polyoctenamer, butyl rubber, halobutyl rubber, polystyreneelastomers, polyethylene elastomers, polyurethane elastomers, polyureaelastomers, metallocene-catalyzed elastomers and plastomers, copolymersof isobutylene and p-alkylstyrene, halogenated copolymers of isobutyleneand p-alkylstyrene, copolymers of butadiene with acrylonitrile,polychloroprene, alkyl acrylate rubber, chlorinated isoprene rubber,acrylonitrile chlorinated isoprene rubber, and combinations of two ormore thereof.

As discussed above, single and multi-layered cores can be made inaccordance with this invention. In two-layered cores, a thermosetmaterial such as, for example, thermoset rubber, can be used to make theouter core layer or a thermoplastic material such as, for example,ethylene acid copolymer containing acid groups that are at leastpartially or fully neutralized can be used to make the outer core layer.Suitable ionomer compositions include partially-neutralized ionomers andhighly-neutralized ionomers (HNPs), including ionomers formed fromblends of two or more partially-neutralized ionomers, blends of two ormore highly-neutralized ionomers, and blends of one or morepartially-neutralized ionomers with one or more highly-neutralizedionomers. Suitable ethylene acid copolymer ionomers and otherthermoplastics that can be used to form the core layer(s) are the samematerials that can be used to make an inner cover layer as discussedfurther below.

In another example, multi-layered cores having an inner core,intermediate core layer, and outer core layer, wherein the intermediatecore layer is disposed between the intermediate and outer core layersmay be prepared in accordance with this invention. More particularly, asdiscussed above, the inner core may be constructed from a thermoplasticor thermoset composition, such as thermoset rubber. Meanwhile, theintermediate and outer core layers also may be formed from thermoset orthermoplastic materials. Suitable thermoset and thermoplasticcompositions that may be used to form the intermediate/outer core layersare discussed above. For example, each of the intermediate and outercore layers may be formed from a thermoset rubber composition. Thus, theintermediate core layer may be formed from a first thermoset rubbercomposition; and the outer core layer may be formed from a secondthermoset rubber composition. In another embodiment, the intermediatecore layer is formed from a thermoset composition; and the outer corelayer is formed from a thermoplastic composition. In a third embodiment,the intermediate core layer is formed from a thermoplastic composition;and the outer core layer is formed from a thermoset composition.Finally, in a fourth embodiment, the intermediate core layer is formedfrom a first thermoplastic composition; and the outer core layer isformed from a second thermoplastic compositions.

In a particular embodiment, the core includes at least one additionalthermoplastic intermediate core layer formed from a compositioncomprising an ionomer selected from DuPont® HPF ESX 367, HPF 1000, HPF2000, HPF AD1035, HPF AD1035 Soft, HPF AD1040, and AD1172 ionomers,commercially available from E. I. du Pont de Nemours and Company. Thecoefficient of restitution (“COR”), compression, and surface hardness ofeach of these materials, as measured on 1.55″ injection molded spheresaged two weeks at 23° C./50% RH, are given in Table 1 below.

TABLE 1 Solid Sphere Solid Sphere Solid Sphere Shore D Example CORCompression Surface Hardness HPF 1000 0.830 115 54 HPF 2000 0.860 90 47HPF AD1035 0.820 63 42 HPF AD1035 Soft 0.780 33 35 HPF AD 1040 0.855 13560 HPF AD1172 0.800 32 37

Cover Layer Structure

The golf balls of this invention further include an outer cover layerpreferably made of a thermoplastic polyurethane composition. In general,polyurethanes contain urethane linkages formed by reacting an isocyanategroup (—N═C═O) with a hydroxyl group (OH). The polyurethanes areproduced by the reaction of a multi-functional isocyanate (NCO—R—NCO)with a long-chain polyol having terminal hydroxyl groups (OH OH) in thepresence of a catalyst and other additives. The chain length of thepolyurethane prepolymer is extended by reacting it with short-chaindiols (OH—R′—OH). The resulting polyurethane has elastomeric propertiesbecause of its “hard” and “soft” segments, which are covalently bondedtogether. This phase separation occurs because the mainly non-polar, lowmelting soft segments are incompatible with the polar, high melting hardsegments. The hard segments, which are formed by the reaction of thediisocyanate and low molecular weight chain-extending diol, arerelatively stiff and immobile. The soft segments, which are formed bythe reaction of the diisocyanate and long chain diol, are relativelyflexible and mobile. Because the hard segments are covalently coupled tothe soft segments, they inhibit plastic flow of the polymer chains, thuscreating elastomeric resiliency.

By the term, “isocyanate compound” as used herein, it is meant anyaliphatic or aromatic isocyanate containing two or more isocyanatefunctional groups. The isocyanate compounds can be monomers or monomericunits, because they can be polymerized to produce polymeric isocyanatescontaining two or more monomeric isocyanate repeat units. The isocyanatecompound may have any suitable backbone chain structure includingsaturated or unsaturated, and linear, branched, or cyclic. Theseisocyanate compounds also can be referred to as polyisocyanates ormulti-functional isocyanates. By the term, “polyamine” as used herein,it is meant any aliphatic or aromatic compound containing two or moreprimary or secondary amine functional groups. The polyamine compound mayhave any suitable backbone chain structure including saturated orunsaturated, and linear, branched, or cyclic. The term “polyamine” maybe used interchangeably with amine-terminated component. Thesepolyamines also can be referred to as amine compounds ormulti-functional amines. By the term, “polyol” as used herein, it ismeant any aliphatic or aromatic compound containing two or more hydroxylfunctional groups. The term “polyol” may be used interchangeably withhydroxy-terminated component. By the term, “polyimine compound”, it ismeant it is meant any aliphatic or aromatic compound containing two ormore imine functional groups. These polyimines also can be referred toas imine compounds or multi-functional imines.

Thermoplastic polyurethanes have minimal cross-linking; any bonding inthe polymer network is primarily through hydrogen bonding or otherphysical mechanism. Because of their lower level of cross-linking,thermoplastic polyurethanes are relatively flexible. The cross-linkingbonds in thermoplastic polyurethanes can be reversibly broken byincreasing temperature such as during molding or extrusion. That is, thethermoplastic material softens when exposed to heat and returns to itsoriginal condition when cooled. On the other hand, thermosetpolyurethanes become irreversibly set when they are cured. Thecross-linking bonds are irreversibly set and are not broken when exposedto heat. Thus, thermoset polyurethanes, which typically have a highlevel of cross-linking, are relatively rigid.

Commercially-available examples of suitable thermoplastic polyurethanesthat can be used in accordance with this invention include TPUs soldunder the tradenames of Texin® 250, Texin® 255, Texin® 260, Texin® 270,Texin®950U, Texin® 970U, Texin®1049, Texin®990DP7-1191, Texin® DP7-1202,Texin®990R, Texin®993, Texin®DP7-1049, Texin® 3203, Texin® 4203, Texin®4206, Texin® 4210, Texin® 4215, and Texin® 3215, each commerciallyavailable from Covestro LLC, Pittsburgh Pa.; Estane® 50 DT3,Estane®58212, Estane®55DT3, Estane®58887, Estane®EZ14-23A, Estane®ETE50DT3, each commercially available from Lubrizol Company of Cleveland,Ohio; and Elastollan®WY1149, Elastollan®1154D53, Elastollan®1180A,Elastollan®1190A, Elastollan®1195A, Elastollan®1185AW,Elastollan®1175AW, each commercially available from BASF; Desmopan® 453,commercially available from Bayer of Pittsburgh, Pa., and the E-SeriesTPUs, such as D 60 E 4024 commercially available from HuntsmanPolyurethanes of Germany.

Aromatic polyurethanes can be prepared in accordance with this inventionand these materials are preferably formed by reacting an aromaticdiisocyanate with a polyol. Suitable aromatic diisocyanates that may beused in accordance with this invention include, for example, toluene2,4-diisocyanate (TDI), toluene 2,6-diisocyanate (TDI), 4,4′-methylenediphenyl diisocyanate (MDI), 2,4′-methylene diphenyl diisocyanate (MDI),polymeric methylene diphenyl diisocyanate (PMDI), p-phenylenediisocyanate (PPDI), m-phenylene diisocyanate (PDI), naphthalene1,5-diisocynate (NDI), naphthalene 2,4-diisocyanate (NDI), p-xylenediisocyanate (XDI), and homopolymers and copolymers and blends thereof.The aromatic isocyanates are able to react with the hydroxyl or aminecompounds and form a durable and tough polymer having a high meltingpoint. The resulting polyurethane generally has good mechanical strengthand cut/shear-resistance.

Aliphatic polyurethanes also can be prepared in accordance with thisinvention and these materials are preferably formed by reacting analiphatic diisocyanate with a polyol. Suitable aliphatic diisocyanatesthat may be used in accordance with this invention include, for example,isophorone diisocyanate (IPDI), 1,6-hexamethylene diisocyanate (HDI),4,4′-dicyclohexylmethane diisocyanate (“H₁₂ MDI”),meta-tetramethylxylyene diisocyanate (TMXDI), trans-cyclohexanediisocyanate (CHDI), and homopolymers and copolymers and blends thereof.Particularly suitable multi-functional isocyanates include trimers ofHDI or H₁₂MDI, oligomers, or other derivatives thereof. The resultingpolyurethane generally has good light and thermal stability.

Any polyol available to one of ordinary skill in the art is suitable foruse according to the invention. Exemplary polyols include, but are notlimited to, polyether polyols, hydroxy-terminated polybutadiene(including partially/fully hydrogenated derivatives), polyester polyols,polycaprolactone polyols, and polycarbonate polyols. In one preferredembodiment, the polyol includes polyether polyol. Examples include, butare not limited to, polytetramethylene ether glycol (PTMEG) which isparticularly preferred, polyethylene propylene glycol, polyoxypropyleneglycol, and mixtures thereof. The hydrocarbon chain can have saturatedor unsaturated bonds and substituted or unsubstituted aromatic andcyclic groups.

In another embodiment, polyester polyols are included in thepolyurethane material. Suitable polyester polyols include, but are notlimited to, polyethylene adipate glycol; polybutylene adipate glycol;polyethylene propylene adipate glycol; o-phthalate-1,6-hexanediol;poly(hexamethylene adipate) glycol; and mixtures thereof. Thehydrocarbon chain can have saturated or unsaturated bonds, orsubstituted or unsubstituted aromatic and cyclic groups. In stillanother embodiment, polycaprolactone polyols are included in thematerials of the invention. Suitable polycaprolactone polyols include,but are not limited to: 1,6-hexanediol-initiated polycaprolactone,diethylene glycol initiated polycaprolactone, trimethylol propaneinitiated polycaprolactone, neopentyl glycol initiated polycaprolactone,1,4-butanediol-initiated polycaprolactone, and mixtures thereof. Thehydrocarbon chain can have saturated or unsaturated bonds, orsubstituted or unsubstituted aromatic and cyclic groups. In yet anotherembodiment, polycarbonate polyols are included in the polyurethanematerial of the invention. Suitable polycarbonates include, but are notlimited to, polyphthalate carbonate and poly(hexamethylene carbonate)glycol. The hydrocarbon chain can have saturated or unsaturated bonds,or substituted or unsubstituted aromatic and cyclic groups. In oneembodiment, the molecular weight of the polyol is from about 200 toabout 4000.

There are two basic techniques that can be used to make thepolyurethanes: a) one-shot technique, and b) prepolymer technique. Inthe one-shot technique, the diisocyanate, polyol, andhydroxyl-terminated chain-extender (curing agent) are reacted in onestep. On the other hand, the prepolymer technique involves a firstreaction between the diisocyanate and polyol compounds to produce apolyurethane prepolymer, and a subsequent reaction between theprepolymer and hydroxyl-terminated chain-extender. As a result of thereaction between the isocyanate and polyol compounds, there will be someunreacted NCO groups in the polyurethane prepolymer. The prepolymershould have less than 14% unreacted NCO groups. Preferably, theprepolymer has no greater than 8.5% unreacted NCO groups, morepreferably from 2.5% to 8%, and most preferably from 5.0% to 8.0%unreacted NCO groups. As the weight percent of unreacted isocyanategroups increases, the hardness of the composition also generallyincreases.

Either the one-shot or prepolymer method may be employed to produce thepolyurethane compositions of the invention. In one embodiment, theone-shot method is used, wherein the isocyanate compound is added to areaction vessel and then a curative mixture comprising the polyol andcuring agent is added to the reaction vessel. The components are mixedtogether so that the molar ratio of isocyanate groups to hydroxyl groupsis preferably in the range of about 1.00:1.00 to about 1.10:1.00. In asecond embodiment, the prepolymer method is used. In general, theprepolymer technique is preferred because it provides better control ofthe chemical reaction. The prepolymer method provides a more homogeneousmixture resulting in a more consistent polymer composition. The one-shotmethod results in a mixture that is inhomogeneous (more random) andaffords the manufacturer less control over the molecular structure ofthe resultant composition.

The polyurethane compositions can be formed by chain-extending thepolyurethane prepolymer with a single chain-extender or blend ofchain-extenders as described further below. As discussed above, thepolyurethane prepolymer can be chain-extended by reacting it with asingle chain-extender or blend of chain-extenders. In general, theprepolymer can be reacted with hydroxyl-terminated curing agents,amine-terminated curing agents, and mixtures thereof. The curing agentsextend the chain length of the prepolymer and build-up its molecularweight. In general, thermoplastic polyurethane compositions aretypically formed by reacting the isocyanate blend and polyols at a 1:1stoichiometric ratio. Thermoset compositions, on the other hand, arecross-linked polymers and are typically produced from the reaction ofthe isocyanate blend and polyols at normally a 1.05:1 stoichiometricratio

A catalyst may be employed to promote the reaction between theisocyanate and polyol compounds for producing the prepolymer or betweenprepolymer and chain-extender during the chain-extending step.Preferably, the catalyst is added to the reactants before producing theprepolymer. Suitable catalysts include, but are not limited to, bismuthcatalyst; zinc octoate; stannous octoate; tin catalysts such asbis-butyltin dilaurate, bis-butyltin diacetate, stannous octoate; tin(II) chloride, tin (IV) chloride, bis-butyltin dimethoxide,dimethyl-bis[1-oxonedecyl)oxy]stannane, di-n-octyltin bis-isooctylmercaptoacetate; amine catalysts such as triethylenediamine,triethylamine, and tributylamine; organic acids such as oleic acid andacetic acid; delayed catalysts; and mixtures thereof. The catalyst ispreferably added in an amount sufficient to catalyze the reaction of thecomponents in the reactive mixture. In one embodiment, the catalyst ispresent in an amount from about 0.001 percent to about 1 percent, andpreferably 0.1 to 0.5 percent, by weight of the composition.

The hydroxyl chain-extending (curing) agents are preferably selectedfrom the group consisting of ethylene glycol; diethylene glycol;polyethylene glycol; propylene glycol; 2-methyl-1,3-propanediol;2-methyl-1,4-butanediol; monoethanolamine; diethanolamine;triethanolamine; monoisopropanolamine; diisopropanolamine; dipropyleneglycol; polypropylene glycol; 1,2-butanediol; 1,3-butanediol;1,4-butanediol; 2,3-butanediol; 2,3-dimethyl-2,3-butanediol;trimethylolpropane; cyclohexyldimethylol; triisopropanolamine;N,N,N′,N′-tetra-(2-hydroxypropyl)-ethylene diamine; diethylene glycolbis-(aminopropyl) ether; 1,5-pentanediol; 1,6-hexanediol;1,3-bis-(2-hydroxyethoxy) cyclohexane; 1,4-cyclohexyldimethylol;1,3-bis-[2-(2-hydroxyethoxy) ethoxy] cyclohexane;1,3-bis-{2-[2-(2-hydroxyethoxy) ethoxy]ethoxy}cyclohexane;trimethylolpropane; polytetramethylene ether glycol (PTMEG), preferablyhaving a molecular weight from about 250 to about 3900; and mixturesthereof.

Suitable amine chain-extending (curing) agents that can be used inchain-extending the polyurethane prepolymer include, but are not limitedto, unsaturated diamines such as 4,4′-diamino-diphenylmethane (i.e.,4,4′-methylene-dianiline or “MDA”), m-phenylenediamine,p-phenylenediamine, 1,2- or 1,4-bis(sec-butylamino)benzene,3,5-diethyl-(2,4- or 2,6-) toluenediamine or “DETDA”,3,5-dimethylthio-(2,4- or 2,6-)toluenediamine, 3,5-diethylthio-(2,4- or2,6-)toluenediamine, 3,3′-dimethyl-4,4′-diamino-diphenylmethane,3,3′-diethyl-5,5′-dimethyl 4,4′-diamino-diphenylmethane (i.e.,4,4′-methylene-bis(2-ethyl-6-methyl-benezeneamine)),3,3′-dichloro-4,4′-diamino-diphenylmethane (i.e.,4,4′-methylene-bis(2-chloroaniline) or “MOCA”),3,3′,5,5′-tetraethyl-4,4′-diamino-diphenylmethane (i.e.,4,4′-methylene-bis(2,6-diethylaniline),2,2′-dichloro-3,3′,5,5′-tetraethyl-4,4′-diamino-diphenylmethane (i.e.,4,4′-methylene-bis(3-chloro-2,6-diethyleneaniline) or “MCDEA”),3,3′-diethyl-5,5′-dichloro-4,4′-diamino-diphenylmethane, or “MDEA”),3,3′-dichloro-2,2′,6,6′-tetraethyl-4,4′-diamino-diphenylmethane,3,3′-dichloro-4,4′-diamino-diphenylmethane,4,4′-methylene-bis(2,3-dichloroaniline) (i.e.,2,2′,3,3′-tetrachloro-4,4′-diamino-diphenylmethane or “MDCA”); andmixtures thereof. One particularly suitable amine-terminatedchain-extending agent is Ethacure 300™ (dimethylthiotoluenediamine or amixture of 2,6-diamino-3,5-dimethylthiotoluene and2,4-diamino-3,5-dimethylthiotoluene.) The amine curing agents used aschain extenders normally have a cyclic structure and a low molecularweight (250 or less).

When the polyurethane prepolymer is reacted with hydroxyl-terminatedcuring agents during the chain-extending step, as described above, theresulting polyurethane composition contains urethane linkages. On theother hand, when the polyurethane prepolymer is reacted withamine-terminated curing agents during the chain-extending step, anyexcess isocyanate groups in the prepolymer will react with the aminegroups in the curing agent. The resulting polyurethane compositioncontains urethane and urea linkages and may be referred to as apolyurethane/urea hybrid. The concentration of urethane and urealinkages in the hybrid composition may vary. In general, the hybridcomposition may contain a mixture of about 10 to 90% urethane and about90 to 10% urea linkages.

More particularly, when the polyurethane prepolymer is reacted withhydroxyl-terminated curing agents during the chain-extending step, asdescribed above, the resulting composition is essentially a purepolyurethane composition containing urethane linkages having thefollowing general structure:

where x is the chain length, i.e., about 1 or greater, and R and R₁ arestraight chain or branched hydrocarbon chain having about 1 to about 20carbons.

However, when the polyurethane prepolymer is reacted with anamine-terminated curing agent during the chain-extending step, anyexcess isocyanate groups in the prepolymer will react with the aminegroups in the curing agent and create urea linkages having the followinggeneral structure:

where x is the chain length, i.e., about 1 or greater, and R and R₁ arestraight chain or branched hydrocarbon chain having about 1 to about 20carbons.

The polyurethane compositions used to form the cover layer may containother polymer materials including, for example: aliphatic or aromaticpolyurethanes, aliphatic or aromatic polyureas, aliphatic or aromaticpolyurethane/urea hybrids, olefin-based copolymer ionomer compositions,polyethylene, including, for example, low density polyethylene, linearlow density polyethylene, and high density polyethylene; polypropylene;rubber-toughened olefin polymers; acid copolymers, for example,poly(meth)acrylic acid, which do not become part of an ionomericcopolymer; plastomers; flexomers; styrene/butadiene/styrene blockcopolymers; styrene/ethylene-butylene/styrene block copolymers;dynamically vulcanized elastomers; copolymers of ethylene and vinylacetates; copolymers of ethylene and methyl acrylates; polyvinylchloride resins; polyamides, poly(amide-ester) elastomers, and graftcopolymers of ionomer and polyamide including, for example, Pebax®thermoplastic polyether block amides, available from Arkema Inc;cross-linked trans-polyisoprene and blends thereof; polyester-basedthermoplastic elastomers, such as Hytrel®, available from DuPont;polyurethane-based thermoplastic elastomers, such as Elastollan®,available from BASF; polycarbonate/polyester blends such as Xylex®,available from SABIC Innovative Plastics; maleic anhydride-graftedpolymers such as Fusabone®, available from DuPont; and mixtures of theforegoing materials.

In addition, the polyurethane compositions may contain fillers,additives, and other ingredients that do not detract from the propertiesof the final composition. These additional materials include, but arenot limited to, catalysts, wetting agents, coloring agents, opticalbrighteners, cross-linking agents, whitening agents such as titaniumdioxide and zinc oxide, ultraviolet (UV) light absorbers, hindered aminelight stabilizers, defoaming agents, processing aids, surfactants, andother conventional additives. Other suitable additives includeantioxidants, stabilizers, softening agents, plasticizers, includinginternal and external plasticizers, impact modifiers, foaming agents,density-adjusting fillers, reinforcing materials, compatibilizers, andthe like. Some examples of useful fillers include zinc oxide, zincsulfate, barium carbonate, barium sulfate, calcium oxide, calciumcarbonate, clay, tungsten, tungsten carbide, silica, and mixturesthereof. Rubber regrind (recycled core material) and polymeric, ceramic,metal, and glass microspheres also may be used. Generally, the additiveswill be present in the composition in an amount between about 1 andabout 70 weight percent based on total weight of the compositiondepending upon the desired properties.

Intermediate Layers

In one preferred embodiment, an intermediate layer is disposed betweenthe single or multi-layered core and surrounding cover layer. Theseintermediate layers also can be referred to as casing or mantle or innercover layers. The intermediate layer can be formed from any materialsknown in the art, including thermoplastic and thermosetting materials,but preferably is formed of an ionomer composition comprising anethylene acid copolymer containing acid groups that are at leastpartially neutralized. Suitable ethylene acid copolymers that may beused to form the intermediate layers are generally referred to ascopolymers of ethylene; C₃ to C₈ α, β-ethylenically unsaturated mono- ordicarboxylic acid; and optional softening monomer. These ethylene acidcopolymer ionomers also can be used to form the inner core and outercore layers as described above. In other embodiments, thesethermoplastic ionomer compositions can be used to make the golf ballcover.

Suitable ionomer compositions include partially-neutralized ionomers andhighly-neutralized ionomers (HNPs), including ionomers formed fromblends of two or more partially-neutralized ionomers, blends of two ormore highly-neutralized ionomers, and blends of one or morepartially-neutralized ionomers with one or more highly-neutralizedionomers. For purposes of the present disclosure, “HNP” refers to anacid copolymer after at least 70% of all acid groups present in thecomposition are neutralized. Preferred ionomers are salts of O/X- andO/X/Y-type acid copolymers, wherein O is an α-olefin, X is a C₃-C₈α,β-ethylenically unsaturated carboxylic acid, and Y is a softeningmonomer. O is preferably selected from ethylene and propylene. X ispreferably selected from methacrylic acid, acrylic acid, ethacrylicacid, crotonic acid, and itaconic acid. Methacrylic acid and acrylicacid are particularly preferred. Y is preferably selected from (meth)acrylate and alkyl (meth) acrylates wherein the alkyl groups have from 1to 8 carbon atoms, including, but not limited to, n-butyl (meth)acrylate, isobutyl (meth) acrylate, methyl (meth) acrylate, and ethyl(meth) acrylate.

Preferred O/X and O/X/Y-type copolymers include, without limitation,ethylene acid copolymers, such as ethylene/(meth)acrylic acid,ethylene/(meth)acrylic acid/maleic anhydride, ethylene/(meth)acrylicacid/maleic acid mono-ester, ethylene/maleic acid, ethylene/maleic acidmono-ester, ethylene/(meth)acrylic acid/n-butyl (meth)acrylate,ethylene/(meth)acrylic acid/isobutyl (meth)acrylate,ethylene/(meth)acrylic acid/methyl (meth)acrylate,ethylene/(meth)acrylic acid/ethyl (meth)acrylate terpolymers, and thelike. The term, “copolymer,” as used herein, includes polymers havingtwo types of monomers, those having three types of monomers, and thosehaving more than three types of monomers. Preferred α, β-ethylenicallyunsaturated mono- or dicarboxylic acids are (meth) acrylic acid,ethacrylic acid, maleic acid, crotonic acid, fumaric acid, itaconicacid. (Meth) acrylic acid is most preferred. As used herein, “(meth)acrylic acid” means methacrylic acid and/or acrylic acid. Likewise,“(meth) acrylate” means methacrylate and/or acrylate.

In a particularly preferred version, highly neutralized E/X- andE/X/Y-type acid copolymers, wherein E is ethylene, X is a C₃-C₈α,β-ethylenically unsaturated carboxylic acid, and Y is a softeningmonomer are used. X is preferably selected from methacrylic acid,acrylic acid, ethacrylic acid, crotonic acid, and itaconic acid.Methacrylic acid and acrylic acid are particularly preferred. Y ispreferably an acrylate selected from alkyl acrylates and aryl acrylatesand preferably selected from (meth) acrylate and alkyl (meth) acrylateswherein the alkyl groups have from 1 to 8 carbon atoms, including, butnot limited to, n-butyl (meth) acrylate, isobutyl (meth) acrylate,methyl (meth) acrylate, and ethyl (meth) acrylate. Preferred E/X/Y-typecopolymers are those wherein X is (meth) acrylic acid and/or Y isselected from (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth)acrylate, methyl (meth) acrylate, and ethyl (meth) acrylate. Morepreferred E/X/Y-type copolymers are ethylene/(meth) acrylic acid/n-butylacrylate, ethylene/(meth) acrylic acid/methyl acrylate, andethylene/(meth) acrylic acid/ethyl acrylate.

The amount of ethylene in the acid copolymer is typically at least 15wt. %, preferably at least 25 wt. %, more preferably least 40 wt. %, andeven more preferably at least 60 wt. %, based on total weight of thecopolymer. The amount of C₃ to C₈ α, β-ethylenically unsaturated mono-or dicarboxylic acid in the acid copolymer is typically from 1 wt. % to35 wt. %, preferably from 5 wt. % to 30 wt. %, more preferably from 5wt. % to 25 wt. %, and even more preferably from 10 wt. % to 20 wt. %,based on total weight of the copolymer. The amount of optional softeningcomonomer in the acid copolymer is typically from 0 wt. % to 50 wt. %,preferably from 5 wt. % to 40 wt. %, more preferably from 10 wt. % to 35wt. %, and even more preferably from 20 wt. % to 30 wt. %, based ontotal weight of the copolymer. “Low acid” and “high acid” ionomericpolymers, as well as blends of such ionomers, may be used. In general,low acid ionomers are considered to be those containing 16 wt. % or lessof acid moieties, whereas high acid ionomers are considered to be thosecontaining greater than 16 wt. % of acid moieties.

The various O/X, E/X, O/X/Y, and E/X/Y-type copolymers are at leastpartially neutralized with a cation source, optionally in the presenceof a high molecular weight organic acid, such as those disclosed in U.S.Pat. No. 6,756,436, the entire disclosure of which is herebyincorporated herein by reference. The acid copolymer can be reacted withthe optional high molecular weight organic acid and the cation sourcesimultaneously, or prior to the addition of the cation source. Suitablecation sources include, but are not limited to, metal ion sources, suchas compounds of alkali metals, alkaline earth metals, transition metals,and rare earth elements; ammonium salts and monoamine salts; andcombinations thereof. Preferred cation sources are compounds ofmagnesium, sodium, potassium, cesium, calcium, barium, manganese,copper, zinc, lead, tin, aluminum, nickel, chromium, lithium, and rareearth metals.

Other suitable thermoplastic polymers that may be used to form theintermediate layer include, but are not limited to, the followingpolymers (including homopolymers, copolymers, and derivatives thereof:(a) polyester, particularly those modified with a compatibilizing groupsuch as sulfonate or phosphonate, including modified poly(ethyleneterephthalate), modified poly(butylene terephthalate), modifiedpoly(propylene terephthalate), modified poly(trimethyleneterephthalate), modified poly(ethylene naphthenate), and those disclosedin U.S. Pat. Nos. 6,353,050, 6,274,298, and 6,001,930, the entiredisclosures of which are hereby incorporated herein by reference, andblends of two or more thereof; (b) polyamides, polyamide-ethers, andpolyamide-esters, and those disclosed in U.S. Pat. Nos. 6,187,864,6,001,930, and 5,981,654, the entire disclosures of which are herebyincorporated herein by reference, and blends of two or more thereof; (c)polyurethanes, polyureas, polyurethane-polyurea hybrids, and blends oftwo or more thereof; (d) fluoropolymers, such as those disclosed in U.S.Pat. Nos. 5,691,066, 6,747,110 and 7,009,002, the entire disclosures ofwhich are hereby incorporated herein by reference, and blends of two ormore thereof; (e) polystyrenes, such as poly(styrene-co-maleicanhydride), acrylonitrile-butadiene-styrene, poly(styrene sulfonate),polyethylene styrene, and blends of two or more thereof; (f) polyvinylchlorides and grafted polyvinyl chlorides, and blends of two or morethereof; (g) polycarbonates, blends ofpolycarbonate/acrylonitrile-butadiene-styrene, blends ofpolycarbonate/polyurethane, blends of polycarbonate/polyester, andblends of two or more thereof; (h) polyethers, such as polyaryleneethers, polyphenylene oxides, block copolymers of alkenyl aromatics withvinyl aromatics and polyamicesters, and blends of two or more thereof;(i) polyimides, polyetherketones, polyamideimides, and blends of two ormore thereof; and (j) polycarbonate/polyester copolymers and blends.

Golf Ball Construction

The solid cores for the golf balls of this invention may be made usingany suitable conventional technique such as, for example, compression orinjection-molding. Typically, the cores are formed by compressionmolding a slug of uncured or lightly cured rubber material into aspherical structure. Prior to forming the cover layer, the corestructure may be surface-treated to increase the adhesion between itsouter surface and adjacent layer. Such surface-treatment may includemechanically or chemically-abrading the outer surface of the core. Forexample, the core may be subjected to corona-discharge,plasma-treatment, silane-dipping, or other treatment methods known tothose in the art.

As discussed above, an inner cover layer or intermediate layer,preferably formed from an ethylene acid copolymer ionomer composition,can be formed between the core or ball sub-assembly and cover layer. Theintermediate layer comprising the ionomer composition may be formedusing a conventional technique such as, for example, compression orinjection-molding. For example, the ionomer composition may beinjection-molded or placed in a compression mold to produce half-shells.These shells are placed around the core in a compression mold, and theshells fuse together to form an intermediate layer. Alternatively, theionomer composition is injection-molded directly onto the core usingretractable pin injection-molding.

Application of Primer, Top-Coats and Isocyanate Treatments

After the golf balls have been removed from the mold, they may besubjected to finishing steps such as flash-trimming, surface-treatment,marking, and application of coatings in accordance with this invention.

For example, in traditional white-colored golf balls, thewhite-pigmented outer cover layer may be surface-treated using asuitable method such as, for example, corona, plasma, or ultraviolet(UV) light-treatment. In another finishing process, the golf balls arepainted with one or more paint coatings. For example, white or clearprimer paint may be applied first to the surface of the ball and thenindicia may be applied over the primer followed by application of aclear polyurethane top-coat. Indicia such as trademarks, symbols, logos,letters, and the like may be printed on the outer cover or prime-coatedlayer, or top-coated layer using pad-printing, ink-jet printing,dye-sublimation, or other suitable printing methods. Any of the surfacecoatings may contain a fluorescent optical brightener.

In one embodiment, a first (primer) polyurethane coating comprisingunreacted isocyanate groups and having an isocyanate index of at leastabout 115 is applied to the outer cover. The golf ball is thenpreferably treated with heat so the coating is at least partially-cured.For example, the golf ball can be heated preferably to a surfacetemperature of at least about 105° to about 200° F. Preferably, the golfball is heated to a surface temperature of about 120° to about 150° F.Preferably, the golf ball is then heated for at a period of 2 minutes toabout 240 minutes, more preferably a period of 4 minutes to 120 minutes,and most preferably about 8 minutes to 60 minutes. In a third step, asecond (top-coat) polyurethane coating is applied to the outer cover.Any suitable coating technique may be used to apply the first and secondpolyurethane coatings. For example, spraying, dipping, brushing, orrolling methods can be used. Then the golf ball can go through a seriesof finishing steps.

In a second embodiment, a first (primer) polyurethane comprisingunreacted isocyanate groups and having an isocyanate index of at leastabout 115 is applied to the outer cover and the golf ball is treatedwith heat as described above. In a third step, a second (top-coat)polyurethane coating having an isocyanate index of less than 96 isapplied to the outer cover.

In a third embodiment, a first (primer) polyurethane comprisingunreacted isocyanate groups and having an isocyanate index of at leastabout 115 and further comprising a catalyst is applied to the outercover and the golf ball is treated with heat as described above. In athird step, a second (top-coat) polyurethane coating is applied to theouter cover as described above. The thermoplastic polyurethanecomposition of the outer cover layer and second (top-coat) polyurethanecoatings also may comprise catalysts. Suitable catalysts include, forexample, dibutyl tin dilaurate, dibutyl tin acetylacetonate, dibutyl tindibutoxide, dibutyl tin sulphide, dibutyl tin di-2-ethylhexanoate,dibutyl tin (IV) diacetate, dialkyltin (IV) oxide, tributyl tinlaurylmercaptate, dibutyl tin dichloride, organo lead, tetrabutyltitanate, tertiary amines, mercaptides, stannous octoate, potassiumoctoate, zinc octoate, diaza compounds, and potassium acetate, andmixtures thereof.

In a fourth embodiment, a mixture comprising a multi-functionalisocyanate and solvent is applied to the outer cover and the golf ballis treated with heat as described above. The mixture also may containadditives such as, for example, ultraviolet (UV) light stabilizers. Afirst (primer) polyurethane coating that may be over-indexed orunder-indexed may be applied to the outer cover. For example, themixture may be over-indexed and comprise unreacted isocyanate groups andhave an isocyanate index of at least about 115. In another example, themixture may be under indexed and have an isocyanate index of less than96. The golf ball is treated with heat as described above. A secondpolyurethane top-coating having an isocyanate index that is over-indexedor under-indexed may be applied. This treatment of the outer cover layerwith isocyanates further enhances cross-linking and improve coverdurability. These isocyanates can function as cross-linkers in thethermoplastic polyurethane cover. The chain length of the thermoplasticpolyurethane is extended and thus the molecular weight of thepolyurethane is increased when treated with the multi-functionalisocyanates.

Isocyanate Indexing: In some embodiments, the cross-linking may takeplace as a result of the relative proportions of isocyanate functionalgroups in the cover layer and the coating layer. As is generally known,polyurethanes (whether thermoplastic or thermoset) are polymerizedthrough the reaction between an isocyanate functional group on apolyisocyanate and a hydroxyl functional group on a polyol. The relativestoichiometric amounts of each of these functional groups is expressedas the “isocyanate index” of the polyurethane system. Namely, theisocyanate index may be expressed as the ratio of the number ofisocyanate groups present in the polyurethane system to the number ofhydroxyl groups times 100. Or, in other words, the isocyanate index maybe expressed as the ratio of the actual number of isocyanate functionalgroups present in the polyurethane system to the hypothetical number ofisocyanate functional groups necessary to fully react with all of thehydroxyl groups present in the polyurethane system.

The isocyanate index may also be referred to as the “NCO index.” Thelocation of the decimal place may vary based on common convention (i.e.the value of the isocyanate index may be equally expressed as 1.00 or100 depending on colloquialism). As used herein, an isocyanate indexvalue of 100 means that the number of isocyanate functional groupspresent in the polyurethane system is equal to the number of hydroxylfunctional groups present in the polyurethane system. An isocyanateindex value of less than 100 means that excess hydroxyl groups arepresent, and an isocyanate index value of greater than 100 means thatexcess isocyanate groups are present.

Preferably, the multi-functional isocyanate compound is selected fromthe group consisting of toluene 2,4-diisocyanate (TDI), toluene2,6-diisocyanate (TDI), 4,4′-methylene diphenyl diisocyanate (MDI),2,4′-methylene diphenyl diisocyanate (MDI), polymeric methylene diphenyldiisocyanate (PMDI), p-phenylene diisocyanate (PPDI), m-phenylenediisocyanate (PDI), naphthalene 1,5-diisocynate (NDI), naphthalene2,4-diisocyanate (NDI), p-xylene diisocyanate (XDI), and isophoronediisocyanate (IPDI), 1,6-hexamethylene diisocyanate (HDI),4,4′-dicyclohexylmethane diisocyanate (“H₁₂ MDI”),meta-tetramethylxylyene diisocyanate (TMXDI), trans-cyclohexanediisocyanate (CHDI), and homopolymers and copolymers and blends thereof.More preferably, the polyisocyanate is selected from the groupconsisting of of 4,4′-methylene diphenyl diisocyanate (MDI),2,4′-methylene diphenyl diisocyanate (MDI), toluene 2,4-diisocyanate(TDI), toluene 2,6-diisocyanate (TDI), 4,4′-dicyclohexylmethanediisocyanate (“H₁₂ MDI”), p-phenylene diisocyanate (PPDI), andisophorone diisocyanate (IPDI), and homopolymers and copolymers andblends thereof.

Generally, the polyurethane coating material may be a two-part coatingsystem. A preferred coating system includes (1) a first part comprisinga polyol or another compound containing an active hydrogen atom, and (2)a second part comprising a polyisocyanate (or polyisocyanurate) with atleast two —N═C═O groups. Suitable polyols for the polyurethane coatingsystem include both polyether and polyester polyols. In one particularembodiment, the polyol may be a hydroxyl functional polyol having ahydroxyl equivalent weight in the range of from about 50 to about 1500,or an hydroxyl equivalent weight being in the range of from about 200 toabout 800. Suitable polyesters for use herein include poly(oxydiethylene adipates) that are condensation products of diethyleneglycol and adipic acid, branched with trimethylolpropane orpentaerythritol, and polycaprolactone (hydroxycaproic acid) polyesters.

The solvent may be any solvent that forms a solution with themulti-functional isocyanate and allows for some level of penetration ofthe isocyanate into the thermoplastic polyurethane substrate to which itis applied. Suitable solvents include, for example, toluene, xylene,naphthalene, ketones, and acetates. Preferably, the solvent comprisesone selected from the group consisting of acetone, methyl ethyl ketone,methyl amyl ketone, dimethyl heptanone, methyl pentanone, methylisobutyl ketone, cyclohexanone, methyl acetate, ethyl acetate, and butylacetate, and mixtures thereof. The mixture preferably comprises fromabout 1 to 25 wt. % isocyanate, and more preferably about 2 to 20 wt. %,and most preferably 5 to 18 wt % isocyanate.

One embodiment of the invention includes a golf ball comprising a singleor dual core and a cover layer formed from a thermoplastic polyurethane(TPU), wherein the TPU cover is not treated with an isocyanate-richcomposition as described above. In another embodiment, the TPU cover istreated with an isocyanate-rich composition as described above.

Post-treatment of molded golf balls having thermoplastic polyurethanecovers with isocyanate-rich and other compositions are described, forexample, in Sullivan and Binette, U.S. Pat. Nos. 10,252,113 and10,363,458 and published U.S. Patent Applications 2019/0083854-A1 and2019/0217157-A1, all of the disclosures of which are incorporated byreference.

Thickness and Hardness of Golf Balls

The golf balls of this invention provide the ball with a variety ofadvantageous mechanical and playing performance properties as discussedfurther below. In general, the hardness, diameter, and thickness of thedifferent ball layers may vary depending upon the desired ballconstruction. If the ball includes an intermediate layer or inner coverlayer, the hardness (material) is about 50 Shore D or greater, morepreferably about 55 Shore D or greater, and most preferably about 60Shore D or greater. In one embodiment, the inner cover has a Shore Dhardness of about 62 to about 90 Shore D. In one example, the innercover has a hardness of about 68 Shore D or greater. In addition, thethickness of the inner cover layer is preferably about 0.015 inches toabout 0.100 inches, more preferably about 0.020 inches to about 0.080inches, and most preferably about 0.030 inches to about 0.050 inches.

The manufacturing methods and molds of this invention may be used tomold relatively thin outer covers, for example covers having a thicknessof less than 0.075 inches, more preferably 0.050 inches and below,preferably 0.040 inches and below, more preferably 0.030 inches andbelow, and most preferably 0.025 inches and below.

More particularly, the outer cover preferably has a thickness within arange having a lower limit of about 0.004 or 0.010 or 0.020 or 0.030 or0.040 inches and an upper limit of about 0.050 or 0.055 or 0.065 or0.070 or 0.080 inches. Most preferably, the thickness of the outer coveris about 0.025 inches or less. The outer cover preferably has a surfacehardness of 65 Shore D or less, or 55 Shore D or less, or 50 Shore D orless, or 50 Shore D or less, or 45 Shore D or less. Preferably, theouter cover has hardness in the range of about 20 to about 59 Shore D.In one example, the outer cover has hardness in the range of about 25 toabout 55 Shore D.

The method of this invention is particularly effective in providing golfballs having a thin outer cover layer. Furthermore, the method of thisinvention provides thin outer covers with substantially uniformthickness. The resulting balls of this invention have good impactdurability and cut/shear-resistance. The United States Golf Association(“USGA”) has set total weight limits for golf balls. Particularly, theUSGA has established a maximum weight of 45.93 g (1.62 ounces) for golfballs. There is no lower weight limit. In addition, the USGA requiresthat golf balls used in competition have a diameter of at least 1.68inches. There is no upper limit so many golf balls have an overalldiameter falling within the range of about 1.68 to about 1.80 inches.The golf ball diameter is preferably about 1.68 to 1.74 inches, morepreferably about 1.68 to 1.70 inches. In accordance with the presentinvention, the weight, diameter, and thickness of the core and coverlayers may be adjusted, as needed, so the ball meets USGA specificationsof a maximum weight of 1.62 ounces and a minimum diameter of at least1.68 inches.

Preferably, the golf ball has a Coefficient of Restitution (COR) of atleast 0.750 and more preferably at least 0.800 (as measured per the testmethods below.) The core of the golf ball generally has a compression inthe range of about 30 to about 130 and more preferably in the range ofabout 70 to about 110 (as measured per the test methods below.) Theseproperties allow players to generate greater ball velocity off the teeand achieve greater distance with their drives. At the same time, therelatively thin outer cover layer means that a player will have a morecomfortable and natural feeling when striking the ball with a club. Theball is more playable and its flight path can be controlled more easily.This control allows the player to make better approach shots near thegreen. Furthermore, the outer covers of this invention have good impactdurability and mechanical strength.

Referring to FIG. 9, a front view of a finished golf ball that can bemade in accordance with this invention is generally indicated at (110).The dimples (112) may have various shapes and be arranged in variouspatterns to modify the aerodynamic properties of the ball. As discussedabove, the polymeric cover material conforms to the interior geometry ofthe mold cavities to form a dimple pattern on the surface of the ball.The mold cavities may have any suitable dimple arrangement such as, forexample, icosahedral, octahedral, cube-octahedral, dipyramid, and thelike. In addition, the dimples may be circular, oval, triangular,square, pentagonal, hexagonal, heptagonal, octagonal, and the like.Possible cross-sectional shapes include, but are not limited to,circular arc, truncated cone, flattened trapezoid, and profiles definedby a parabolic curve, ellipse, semi-spherical curve, saucer-shapedcurve, sine or catenary curve, or conical curve. Other possible dimpledesigns include dimples within dimples, constant depth dimples, ormulti-lobe dimples. It also should be understood that more than oneshape or type of dimple may be used on a single ball, if desired. Thetotal number of dimples on the ball, or dimple count, may vary dependingsuch factors as the sizes of the dimples and the pattern selected.Dimple patterns that provide a high percentage of surface coverage arepreferred.

As shown in FIG. 10, a two-piece golf ball (114) can be made having acore (116) and a surrounding thermoplastic polyurethane outer coverlayer (118). In the golf ball (114), the core (116) has a relativelylarge diameter and the outer cover (118) has a relatively smallthickness. Referring to FIG. 11, in another embodiment, a two-piece golfball (120) having a smaller core (122) and a thicker outer cover layer(124) can be made. Turning to FIG. 12, a three-piece golf ball (126) ismade, wherein the dual-layered core (inner core (128) and outer corelayer (130) is surrounded by a single-layered thermoplastic polyurethanecover (132).

In FIG. 13, a partial cut-away view of a three-piece golf ball (142)having an inner core (144), outer core (146) and surroundingthermoplastic polyurethane cover (148) is shown. Finally, in FIG. 14, afour-piece ball (150) containing a dual-core having an inner core (152)and outer core layer (154) is shown. The dual-core is surrounded by amulti-layered cover with an inner cover layer (156) and thermoplasticpolyurethane outer cover (160).

It should be understood that the golf balls shown in FIGS. 1-14 are forillustrative purposes only, and they are not meant to be restrictive.Other mold and golf ball constructions can be made in accordance withthis invention.

When numerical lower limits and numerical upper limits are set forthherein, it is contemplated that any combination of these values may beused. Other than in the operating examples, or unless otherwiseexpressly specified, all of the numerical ranges, amounts, values andpercentages such as those for amounts of materials and others in thespecification may be read as if prefaced by the word “about” even thoughthe term “about” may not expressly appear with the value, amount orrange. Accordingly, unless indicated to the contrary, the numericalparameters set forth in the specification and attached claims areapproximations that may vary depending upon the desired propertiessought to be obtained by the present invention.

It is understood that the manufacturing methods, mold apparatus,compositions, constructions, and products described and illustratedherein represent only some embodiments of the invention. It isappreciated by those skilled in the art that various changes andadditions can be made to methods, mold apparatus, compositions,constructions, and products without departing from the spirit and scopeof this invention. It is intended that all such embodiments be coveredby the appended claims.

We claim:
 1. A method for molding a golf ball, comprising the steps of:providing a mold having a lower mold cavity and upper mold cavity, eachmold cavity having an arcuate inner surface defining an inverted dimplepattern; so that when the upper and lower mold cavities are matedtogether, they define a mold having an interior spherical cavity forholding a golf ball subassembly; loading the golf ball subassembly intothe interior spherical cavity of the mold, wherein the mold furtherincludes two or more retractable pins for holding the golf ball withinthe spherical cavity, each retractable pin having a primary ventsection, secondary vent section, and tertiary vent section, the primaryvent being in fluid connection with the secondary vent and the secondaryvent being in fluid connection with the tertiary vent for removinggasses from the interior spherical cavity; injecting a polymericmaterial into the spherical cavity to form a spherical cover over thegolf ball sub-assembly; detaching the lower and upper mold cavities andremoving the molded golf ball from the mold.
 2. The method of claim 1,wherein the retractable pin has a free-end planar surface and the pin ismovable between an extended position, wherein the free end surfacecontacts the ball subassembly and a retracted position wherein theplanar surface forms a portion of the inner wall of the inner surface ofthe mold cavity.
 3. The method of claim 1, wherein the retractable pinhas an upper region and the primary vent is a channel defined along aside of the upper region.
 4. The method of claim 1, wherein theretractable pin has an upper region and the primary vent is anon-channel and defined along the upper region, the upper region havinga diameter that is less than the diameter of a bore in the mold cavityfor inserting the pin.
 5. The method of claim 1, wherein the secondaryvent is an elliptical-shaped channel that is positioned below theprimary vent and extends around the perimeter of the retractable pin. 6.The method of claim 5, wherein the gasses enter the secondary vent andflow through the elliptical-shaped channel and around the perimeter ofthe retractable pin.
 7. The method of claim 1, wherein the tertiary ventis a channel that is positioned below the secondary vent and is definedalong a side of the retractable pin.
 8. The method of claim 1, whereinthe mold further includes one stationary center venting pin.
 9. Themethod of claim 8, wherein the mold further includes two or morestationary inner venting pins, the inner venting pins surrounding thestationary center pin.
 10. The method of claim 9, wherein the moldfurther includes two or more stationary outer venting pins, the outerventing pins surrounding the inner venting pins.
 11. The method of claim1, wherein the polymeric material is a thermoplastic polyurethanecomposition.
 12. The method of claim 1, wherein the polymeric materialis thermoplastic ethylene acid copolymer ionomer composition.
 13. Themethod of claim 1, wherein the ball subassembly comprises a core formedfrom a polybutadiene rubber composition.
 14. The method of claim 1,wherein the ball subassembly comprises a core formed from apolybutadiene rubber composition, and an intermediate layer formed froman ethylene acid copolymer ionomer composition.
 15. A mold for forming agolf ball cover, the mold comprising: a lower hemispherical-shaped moldcavity; an upper hemispherical-shaped mold cavity; each mold cavityhaving an arcuate inner surface defining an inverted dimple pattern; sothat when the upper and lower mold cavities are mated together, theydefine a mold having an interior spherical cavity for holding a golfball subassembly; and each mold cavity comprising at least oneretractable pin for holding the golf ball within the spherical cavity,each retractable pin having a primary vent section, secondary ventsection, and tertiary vent section, the primary vent being in fluidconnection with the secondary vent and the secondary vent being in fluidconnection with the tertiary vent for removing gasses from the interiorspherical cavity.
 16. The mold of claim 15, wherein the retractable pinhas a free-end planar surface and the pin is movable between an extendedposition, wherein the free end surface contacts the ball subassembly anda retracted position wherein the planar surface forms a portion of theinner wall of the inner surface of the mold cavity.
 17. The mold ofclaim 15, wherein the retractable pin has an upper region and theprimary vent is a channel defined along a side of the upper region. 18.The mold of claim 15, wherein the retractable pin has an upper regionand the primary vent is a non-channel and defined along the upperregion, the upper region having a diameter that is less than thediameter of a bore in the mold cavity for inserting the pin.
 19. Themold of claim 15, wherein the secondary vent is an elliptical-shapedchannel that is positioned below the primary vent and extends around theperimeter of the retractable pin.
 20. The mold of claim 19, wherein thegasses enter the secondary vent and flow through the elliptical-shapedchannel and around the perimeter of the retractable pin.
 21. The mold ofclaim 15, wherein the tertiary vent is a channel that is positionedbelow the secondary vent and is defined along a side of the retractablepin.